In a conventional method where transmission information is allocated into a plurality of subcarriers, while a frequency diversity effect may be expected, a burden of signaling for connection control and allocation control of radio resources may be disadvantageously increased. When an amount of transmitting/receiving information is increased, the overhead is relatively increased and the capacity is reduced. Further, when a packet is not correctly received, retransmission process becomes necessary. As a result, the number of transmissions is increased and the overhead is further increased.
To reduce the increase of the overhead due to the transmitting/receiving control information, there is proposed a method of changing a length of the Transmission Time Interval (TTI) in, for example, 3GPP TSG-RAN Joint WG1/WG2, Athens, Greece, 27-31, March 2006, R2-060868. In this document, while the allocation of frequency resources and a modulation method are left unchanged, the TTI length is increased by transmitting data blocks for a transport channel (transport blocks) by use of a plurality of subframes. In this method, for example, when the TTI length is multiplied by “N” times (using sequential N subframes), the amount of control information for a layer 1 is reduced by approximately “1/N”.
On the other hand, there is proposed another method of changing the TTI length in accordance with a packet size in, for example, 3GPP TSG-RAN WG2 #52, Athens, Greece, 27-31 Mar. 2006, R2-060944. In this method, it is not necessary to divide a packet into a prescribed TTI length (such as the length of one subframe). As a result, a burden of signaling for controlling information may be reduced.